/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification of Java bytecode.
 *
 * Copyright (c) 2002-2018 GuardSquare NV
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.classfile.attribute.preverification;

import proguard.classfile.*;
import proguard.classfile.attribute.CodeAttribute;
import proguard.classfile.attribute.preverification.visitor.StackMapFrameVisitor;

/**
 * This abstract class represents a stack map frame. Specific types of entries are subclassed from it.
 *
 * @author Eric Lafortune
 */
public abstract class StackMapFrame implements VisitorAccepter {
    public static final int SAME_ZERO_FRAME = 0;
    public static final int SAME_ONE_FRAME = 64;
    public static final int SAME_ONE_FRAME_EXTENDED = 247;
    public static final int LESS_ZERO_FRAME = 248;
    public static final int SAME_ZERO_FRAME_EXTENDED = 251;
    public static final int MORE_ZERO_FRAME = 252;
    public static final int FULL_FRAME = 255;

    public int u2offsetDelta;

    /**
     * An extra field in which visitors can store information.
     */
    public Object visitorInfo;

    /**
     * Returns the bytecode offset delta relative to the previous stack map frame.
     */
    public int getOffsetDelta() {
        return u2offsetDelta;
    }

    // Abstract methods to be implemented by extensions.

    /**
     * Returns the stack map frame tag that specifies the entry type.
     */
    public abstract int getTag();

    /**
     * Accepts the given visitor.
     */
    public abstract void accept(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset,
        StackMapFrameVisitor stackMapFrameVisitor);

    // Implementations for VisitorAccepter.

    public Object getVisitorInfo() {
        return visitorInfo;
    }

    public void setVisitorInfo(Object visitorInfo) {
        this.visitorInfo = visitorInfo;
    }

    // Implementations for Object.

    public boolean equals(Object object) {
        if (object == null || this.getClass() != object.getClass()) {
            return false;
        }

        StackMapFrame other = (StackMapFrame)object;

        return this.u2offsetDelta == other.u2offsetDelta;
    }

    public int hashCode() {
        return getClass().hashCode() ^ u2offsetDelta;
    }

    public String toString() {
        return "[" + u2offsetDelta + "] ";
    }
}
